Thermal Stability of Quasi-1D NbS₃ Nanoribbons and Their Transformation to 2D NbS₂: Insights from in Situ Electron Microscopy and Spectroscopy

Abstract

In situ electron microscopy imaging and spectroscopy enabled us to study the evolution of quasi-1D NbS3-IV nanoribbons with respect to morphology and chemical structure at temperatures between room temperature and 1000 °C. Scanning transmission electron microscopy (STEM) experiments included imaging in the secondary electron, (transmitted) bright field, and high-angle annular dark-field modes while operating in the low kV regime. The results showed that NbS3-IV samples transform dramatically from smooth nanoribbons into highly textured configurations featuring polyhedral divots and steps. Similar in situ heating experiments conducted with aberration-corrected STEM revealed that bilayers of NbS3-IV chains convert topotactically into aligned 2H-NbS2 sheets upon loss of sulfur. Atomic resolution imaging, fast Fourier transform analysis, and electron energy loss spectroscopy confirmed these chemical changes, from which we propose an atomistic mechanism for the NbS3-IV → 2H-NbS2 conversion.

Single Quasi-1D Chains of Sb2Se3 Encapsulated Within Carbon Nanotubes

“…Beyond the directed growth of 2D vdW crystals along 1D, recent years have seen a growing interest in the creation and rediscovery of crystals that are comprised of 1D or q-1D chains with sub-nanometer cross sections held together by weak vdW interactions. [22][23][24][25][26][27][28] Owing to the one-dimensional nature of these crystals, emergent properties such as higher-order topological states, 2,27,29 Dirac polarons, 30 controllable charge density waves, 26 high-fidelity electron transport, 23 excitonic insulating states, 31 and even unconventional superconductivity 32,33 have been demonstrated. Furthermore, the vdW nature of these families of 1D and q-1D vdW crystals has allowed for the implementation of top-down exfoliation routes previously established for 2D vdW crystals to access ultrathin nanostructures approaching sub-10 nm thicknesses.…”

Studying the Effect of Oxidation on the Thermolysis of (NH4)2WS4 with In‐ and Ex‐Situ Electron Microscopy

“…Beneficially, this allowed us not only to view the internal structural changes that occurred with BF and HAADF images, but also to track morphology changes with the SE detector as the precursor was heated. [13] By combining these in situ results with energy dispersive X-ray spectroscopy maps and atomic resolution STEM images taken ex situ of the end-product, we could clearly see the vast differences that oxidization of the precursor plays during thermolysis as well as the impact of the precursor concentration on the chip. Advantageously, the resultant nanomaterials that formed are primarily 1D and 2D WO 3 nanostructures, which are also sought-after metal oxides, showing that this route is a useful methodology for their generation.…”

“…For example, addition of potassium into the precursor induced a more vertical growth in WS 2 crystals compared to its pure counterpart. [13] It should be noted that in these previous cases, pristine precursors such as (NH 4 ) 2 WS 4 are used during thermolysis with little mentioned regarding what may occur to the overall reaction pathways and nanostructures being formed on account of precursor oxidation. This is unfortunate, as oxidation of precursor chemicals is one of the most common means of contamination as well as a general concern since metal chalcogenides are highly susceptible to material degradation due to oxidation.…”

“…When impurities were added to the thermolysis reaction, varying crystal growth dynamics also occurred. For example, addition of potassium into the precursor induced a more vertical growth in WS 2 crystals compared to its pure counterpart [13] . It should be noted that in these previous cases, pristine precursors such as (NH 4 ) 2 WS 4 are used during thermolysis with little mentioned regarding what may occur to the overall reaction pathways and nanostructures being formed on account of precursor oxidation.…”

Single Quasi-1D Chains of Sb2Se3 Encapsulated within Carbon Nanotubes

“…Most recently, there has been a growing interest in the creation and rediscovery of crystals with even lower dimensions and comprising vdW-bound one-dimensional (1D) or quasi-1D (q-1D) chains with subnanometer cross-sections. − Owing to the 1D character of these crystals, emergent properties such as higher-order topological states, ,, Dirac polarons, controllable charge density waves, high-fidelity electron transport, excitonic insulating states, and even unconventional superconductivity , have been demonstrated. Furthermore, the vdW nature of these 1D and q-1D vdW crystals has allowed for the implementation of top-down exfoliation routes previously established for 2D vdW crystals to access ultrathin nanostructures approaching sub-10 nm thicknesses. ,− While these strategies have been successful, controlling the size distribution and morphology of the resulting nanostructures remains a challenge and often results in a combination of nanowires, nanoribbons, or nanosheets.…”